The present invention relates to a plasma processing apparatus and a processing method for performing processing such as etching using plasma formed in a processing chamber inside a vacuum container by mounting a sample, which is a substrate such as a semiconductor wafer, on an upper surface of a sample stage arranged in the processing chamber, and relates to a plasma processing apparatus and a plasma processing method for performing the processing while making a refrigerant flow through refrigerant channels inside the sample stage included in a refrigeration cycle to adjust a temperature of the sample stage.
Conventionally, in semiconductor device manufacturing processes, plasma processing is performed on a sample such as a semiconductor wafer by means of a plasma etching apparatus or a plasma CVD apparatus. In these types of plasma processing, the temperature of the sample largely affects the result of the processing. More specifically, in plasma etching, the temperature of the sample affects the resulting dimensions and/or shape of a pattern formed at a surface of the sample by etching, and in plasma CVD processing, the temperature of the sample affects the quality and/or film formation rate of a film formed on a surface of the sample. Therefore, in these types of plasma processing, in order to enhance the quality of processing performed on a surface of the sample substrate, it is very important to manage the temperature of the sample.
In these types of plasma processing, in order to control the temperature of a sample, techniques in which the temperature inside a sample stage that holds a sample and the temperature of a sample holding surface are adjusted by means of a temperature adjustment unit arranged inside the sample stage have been employed. For example, an apparatus system in which refrigerant channels are formed inside a sample stage and a liquid refrigerant is made to flow in the channels to adjust the temperature of the sample stage by means of heat transfer, whereby the sample is adjusted to a desired temperature, is used. In such case, a refrigerant temperature adjusted to a desired temperature, is used. In such case, a refrigerant temperature adjustment section (for example, a chiller unit) is connected to the sample stage via pipings, a refrigerant adjusted to a predetermined temperature by a cooling apparatus or a heating apparatus inside the refrigerant temperature adjustment section is supplied into the channels inside the sample stage, and absorbs heat input from plasma and then is returned to the refrigerant temperature adjustment section.
Such refrigerant temperature adjustment section is configured so as to temporarily store the liquid refrigerant in a refrigerant storage tank and adjust the temperature of the refrigerant and then supplies the refrigerant to the sample stage. In this configuration, since a large quantity of refrigerant is used for temperature adjustment, the heat capacity of the refrigerant is large, and thus, the configuration is advantageous in maintaining the temperature of the sample constant even if the amount of heat input to the sample and the sample stage is changed. However, an attempt to largely and promptly change the temperatures of the sample and the sample stage in an active manner causes the problem of difficulty in prompt temperature change because of the large heat capacity of the refrigerant. Furthermore, heat exchange between the liquid refrigerant and the channels is performed only by means of heat transfer and thus, a small quantity of heat transfer is also one of causes that hinder prompt change in temperature of the sample stage and the sample.
Meanwhile, along with an increase in diameter of semiconductor wafers, which are samples, in the aforementioned plasma processing in semiconductor device manufacturing, power applied to the samples during the processing has been increasing, and as a result, the amount of heat input to the sample and the sample stage has become larger than ever. Therefore, there is a demand for a technique that stably adjusts the temperature of a semiconductor substrate at high speed and with high accuracy even upon input of a large amount of heat. Furthermore, because of the growing complexity of semiconductor device structures as well as provision of multiple layers on semiconductor substrate surface, it is desired to promptly and properly adjust the temperature of a sample according to each of processing steps that process respective films.
For responding to the above issues, direct expansion-type refrigerant temperature adjustment techniques have been proposed. In the expansion-type refrigerant temperature adjustment techniques, a path in which a refrigerant for adjusting a temperature of a sample stage is circulated is configured as a heat cycle including a compressor, a condenser, an expansion valve and an evaporator, and the refrigerant is brought to boiling and evaporated in refrigerant channels in the sample stage, whereby the sample stage acts as an evaporator in the heat cycle. As an example of such techniques, that disclosed in JP-A-2008-34409 (corresponding to U.S. Pat. No. 7,838,792) is known.